Yamaha TZM 150 Riders

[supafly]

hmmm... ori stock airbox how much? my meter dun hav the reset knob... wakakakak! ah... tzm pipe ori stock how much?

[hohosaint]

Originally posted by supafly@Jun 23 2005, 09:08 AM

hmmm... ori stock airbox how much? my meter dun hav the reset knob... wakakakak! ah... tzm pipe ori stock how much?

Your pipe spoiled? And why you wanna change airbox... Too many holes ar? keke... Meter i Know.

[speedkills]

hmmm...bike coming home late...because if come home today,insurance will be higher...monday then come home...heh=)

[hohosaint]

For those who want to modify their tzms.

 

 

CYLINDER PORTING

 

The cylinder ports are designed to produce a certain power characteristic over a fairly narrow rpm band. Porting or tuning is a metal machining process performed to the cylinder ports (exhaust & transfers) that alters the timing, area size, and angles of the ports in order to adjust the power band to better suit the rider's demands. For example, a veteran trail rider riding an RM250 in the Rocky mountain region of the USA will need to adjust the power band for more low end power because of the steep hill climbs and the lower air density of higher altitudes. The only way to determine what changes will be needed to the engine is by measuring and calculating the stock engine's specifications. The most critical measurement is termed port-time-area. This term is a calculation of a port's size area and timing in relation to the displacement of the engine and the rpm. Experienced tuners know what the port-time-area values of the exhaust and transfer ports should be for an engine used for a particular purpose. In general, if a tuner wants to adjust the engine's power band for more low to mid range he would do the following things. Turn down the cylinder base on a lathe to increase the effective stroke (distance from TDC to exhaust port opening). This also retards the exhaust port timing and shortens the duration and increases the compression ratio. Next the transfer ports should be narrowed and re-angled with epoxy to reduce the port-time-area for an rpm peak of 7,000 rpm. The rear transfer ports need to be re-angled so they oppose each other rather than pointing forward to the exhaust port. This changes the loop scavenging flow pattern of the transfer ports to improve scavenging efficiency at low to mid rpm (2,000 to 5,000 rpm). An expert rider racing mx in England would want to adjust the power band of an RM250 for more mid to top end power. The cylinder would need to be tuned radically different than for trail riding.

 

Here is an example. The exhaust port would have to be raised and widened to change the port-time-area peak for a higher rpm (9,000 rpm). For either of these cylinder modifications to be effective, other engine components would also need to be changed to get the desired tuning effect.

 

 

 

CYLINDER HEAD

 

Cylinder heads can be reshaped to change the power band. Generally speaking, a cylinder head with a small diameter and deep combustion chamber, and a wide squish band (60% of the bore area). Combined with a compression ratio of 9 to 1 is ideally suited for low to mid range power. A cylinder head with a wide shallow chamber and a narrow squish band (35-45% of bore area) and a compression ratio of 8 to 1, is ideally suited for high rpm power.

 

There are many reasons why a particular head design works for certain types of racing. For example; a head with a wide squish band and a high compression ratio will generate high turbulence in the combustion chamber. This turbulence is termed Maximum Squish Velocity, MSV is rated in meters per second (m/s). A cylinder head designed for supercross should have an MSV rating of 28m/s. Computer design software is used to calculate the MSV for head designs. In the model tuning tips chapters of this book, all the head specs quoted have MSV ratings designed for the intended power band changes.

 

 

 

CRANKSHAFT

 

There are two popular mods hop-up companies are doing to crankshafts; stroking and turbo-vaning. Stroking means to increase the distance from the crank center to the big end pin center. There are two techniques for stroking crankshafts; weld old hole and re-drill a new big end pin hole, or by installing an off-set big end pin. The method of weld and re-drilling is labor intensive. The off-set pin system is cheap, non-permanent, and can be changed quickly. In general, increasing the stroke of a crankshaft boosts the mid range power but decreases the engine's rpm peak.

 

The term "Turbo-Crank" refers to a modification to the crankshaft of a two-stroke engine, whereby scoops are fastened to the crank in order to improve the volumetric efficiency of the engine. Every decade some hop-up shop revives this old idea and gives it a trendy name with product promises that it can't live up to. These crank modifications cause oil to be directed away from the connecting rod and often times the vanes will detach from the crank at high rpm, causing catastrophic engine damage.

 

 

CARBURETOR

 

In general a small diameter carburetor will have high velocity and a good flow characteristic for a low to mid rpm power band. A large diameter carburetor works better for high rpm power bands. For 125 cc engines a 34mm carburetor works well for supercross and enduro and a 36 or 338 mm carburetor works best for fast mx tracks. For 250 cc engines a 36 mm carburetor works best for low to mid power bands and a 39.5 mm carburetor works best for top end power bands. Recently there has been a trend in the use of air-foils and rifle-boring for carbs. These innovations are designed to improve air flow at low throttle openings. Some companies sell carb inserts, to change the diameter of a carb. Typically a set of inserts is sold with a service of over boring the carb. For example; a carb for a 250cc bike (38mm) will be bored to 39.5mm and two inserts will be supplied. The carb can then be restricted to a diameter of 36 or 38mm.

 

 

 

REED VALVE

 

Think of a reed valve like a carburetor, bigger valves with large flow-areas work best for high rpm power bands. In general, reed valves with six or more petals are used for high rpm engines. Reed valves with four petals are used for dirt bikes that need strong low end and mid range power. There are three other factors to consider when choosing a reed valve. The angle of the reed valve, the type of reed material, and the petal thickness. The two common reed valve angles are 30 and 45 degrees. A 30-degree valve is designed for low to mid rpm and a 45 degree valve is designed for high rpm. There are two types of reed petal materials commonly used, carbon fiber and fiberglass. Carbon fiber reeds are lightweight but relatively stiff (spring tension) and designed to resist fluttering at high rpm. Fiberglass reeds have relatively low spring tension so they instantly respond to pressure that changes in the crankcase, however the low spring tension makes them flutter at high rpm thereby limiting the amount of power. Fiberglass reed petals are good for low to mid power bands and carbon fiber reeds are better for high rpm engines.

 

Boyesen Dual Stage reeds have a large thick base reed with a smaller thinner reed mounted on top. This setup widens the rpm range where the reed valve flows best. The thin reeds respond to low rpm and low frequency pressure pulses. The thick reeds respond to higher-pressure pulses and resist fluttering at high rpm. A Boyesen RAD valve is different than a traditional reed valve. Bikes with single rear shocks have off-set carbs. The RAD valve is designed to redistribute the gas flow to the crankcases evenly. A RAD valve will give an overall improvement to the power band. Polini of Italy makes a reed valve called the Supervalve. It features several mini sets of reeds positioned vertically instead of horizontally like conventional reed valves. These valves are excellent for enduro riding because of improved throttle response. In tests on an inertia chassis dyno show the Supervalve to be superior when power shifting. However these valves don't generate greater peak power than conventional reed valves. Supervalves are imported to America and sold by Moto Italia in Maine.

 

 

 

EXHAUST PIPE

 

The exhaust pipe of a two-stroke engine attempts to harness the energy of the pressure waves from combustion. The diameter and length of the five main sections of a pipe, are critical to producing the desired power band. The five sections of the pipe are the head pipe, diffuser cone, dwell, baffle cone, and the stinger. In general, after market exhaust pipes shift the power band up the rpm scale. Most pipes are designed for original cylinders not tuned cylinders. Companies like MOTOWERKS custom computer design and fabricate pipes based on the cylinder specifications and the type of power band targeted.

 

 

 

SILENCER

 

Silencers come in all sorts of shapes and sizes. A long silencer with a small diameter enhance the low to mid power because it increases the bleed-down pressure in the pipe. A silencer with a short length and a large core diameter provides the best bleed-down pressure for a high rpm engine. Too much pressure in the pipe at high rpm will radically increase the temperature of the piston crown and could cause the piston to seize in the cylinder.

 

 

 

TIPS FOR BIG BORING CYLINDERS

 

In the mid nineties, European electro-plating companies started service centers in America. This made it possible to over bore cylinders and electro-plate them to precise tolerances. This process is used by tuners to push an engine's displacement to the limit of the racing class rules, or make the engine legal for a different class.

 

When you change the displacement of the cylinder, there are so many factors to consider. Factors like; port-time-area, compression ratio, exhaust valves, carb jetting, silencer, and ignition timing. Here is an explanation of what you need to do when planning to over bore a cylinder.

 

Port-Time-Area - This is the size and opening timing of the exhaust and intake ports, versus the size of the cylinder and the rpm. When increasing the displacement of the cylinder, the cylinder has to be bored to a larger diameter. The ports enter the cylinder at angles of approximately 15 degrees. When the cylinder is bore is made larger, the transfer ports drop in height and retard the timing and duration of those ports. The exhaust port gets narrower. If you just over bored and plated a cylinder, it would have much more low end power than stock. Normally tuners have to adjust the ports to suit the demands of the larger engine displacement. Those exact dimension changes can be determined with TSR's Time-Area computer program.

 

Cylinder Head - The head's dimensions must be changed to suit the larger piston. The bore must be enlarged to the finished bore size. Then the squish band deck height must be set to the proper installed squish clearance. The larger bore size will increase the squish turbulence so the head's squish band may have to be narrowed. The volume of the head must be increased to suit the change in cylinder displacement. Otherwise the engine will run flat at high rpm or ping in the mid range from detonation.

 

Exhaust Valves - When the bore size is increased, the exhaust valve to piston clearance must be checked and adjusted. This pertains to the types of exhaust valves that operate within close proximity of the piston. If the exhaust valves aren't modified, the piston could strike the valves and cause serious engine damage.

 

Carb - The piston diameter and carb bore diameter are closely related. The larger the ratio between the piston size and the carb size, the higher the intake velocity. That makes the jetting richer. Figure on leaning the jetting after an engine is over bored.

 

Ignition Timing - The timing can be retarded to improve the over rev. Normally over bored engines tend to run flat on top end.

 

Pipe and Silencer - Because only the bore size is changed, you won't need a longer pipe only one with a larger center section. Some riders use silencers that are shorter with larger outlets to adjust the back-pressure in the pipe for the larger engine displacement.

 

For reading purposes.

[hmmm]

Gewd Information :thumb:

 

but rather to chim ah

[sian ar]

wah......juz nw saw crossovers tzm so beautiful n nice sak.... very2 the nice sia........

[speedkills]

wa hoho...bike encyclopedia....... so long..see le also

[speedkills]

wa....so quiet..............................................................

 

anyone wanna go to yishun dam tonight? i be going ther...going down town first tho...anyone interested jus drop me a call...

 

91060925 yandao.

[CrossOver]

Originally posted by sian ar@Jun 23 2005, 10:17 PM

wah......juz nw saw crossovers tzm so beautiful n nice sak.... very2 the nice sia........

HAHA.. ok ok only ah.. Just another makeover..

[sian ar]

eh cross over u nvr change footrest ar coz me saw on the left side got something missing hehehehe... after seeing ur bike makes me wanna send mine 4 respray

[CrossOver]

HAHA.. Nope.. I never change.. Just grind it shot.. Both side is missing the black slider.. HAHA.. But so far so good.. Used to small foot rest.. Will upload my new bike pic soon

[phill]

ask u guys .. if u buy chamber from msia then wad abt ur original pipe?, throw away ? or put at the bikeshop ?

 

or u guys buy chamber at sg?

[CrossOver]

U got a buddy?? Get a pillion, wrap ur original and ask him to help hold.. If u know the mechanic there, u can ask him to hold it for u, like i did before..

[speedkills]

yeah!! tp on 13th july!!!! woooohoooooooooooooooooooooo :thumb:

[supafly]

wah so fast sia speedkills! good luck!

[speedkills]

Originally posted by supafly@Jun 25 2005, 01:04 AM

wah so fast sia speedkills! good luck!

thank you..... heh....ok la...wher got fast....Tp mus pass then maybe fast

[RedHare]

Who selling exhaust pipe??? I wan I wan? I wan a Org exhaust pipe best if without mob.

[hmmm]

All the best for yr TP.... :thumb:

[speedkills]

Originally posted by hmmm@Jun 25 2005, 06:42 AM

All the best for yr TP.... :thumb:

thanks thanks

[speedkills]

haiyoh so quiet....

 

anyone wanna take up drums or guitar lessons can find me...i give private/group lessons. heh

 

jus let me know.

[QuoVadis]

people. Question!!!

 

When i throttle, somewhere in my tank got this loose metal sound. My fren said wat bearing spoil/loose. How 2 verify? if like tt how much est to change ah? cos the sound very irritating. haha. cheers !

[CrossOver]

Originally posted by QuoVadis@Jun 26 2005, 12:46 AM

people. Question!!!

 

When i throttle, somewhere in my tank got this loose metal sound. My fren said wat bearing spoil/loose. How 2 verify? if like tt how much est to change ah? cos the sound very irritating. haha. cheers !

Hard to say.. If got that sound, could be anything.. Everywhere in ur bike is metal.. HEHE.. The next time u ride try to pinpoint further..

[QuoVadis]

Hhahaha.. but all i could guess was somewhere from the engine side. AH!!! Got this ball sound moving loosely like the ball from a marker pen. hahahaha.

[hmmm]

Originally posted by QuoVadis@Jun 26 2005, 12:46 AM

people. Question!!!

 

When i throttle, somewhere in my tank got this loose metal sound. My fren said wat bearing spoil/loose. How 2 verify? if like tt how much est to change ah? cos the sound very irritating. haha. cheers !

 

 

 

It might be yr piston ring go shop ask ah

 

easy?? but bcareful some might say this n tat.... juz go a few shops to eliminate

 

the fake ones...

[QuoVadis]

alamakkkk.. wat mite happen to the piston ring?